1. Technical Field
The present invention relates to liquid crystal devices for use in displaying various types of information and to electronic apparatuses.
2. Related Art
Generally, liquid crystal display modes can be classified into the following three types: twisted nematic (TN) mode; vertical alignment mode intended to increase the viewing angle and contrast; and transverse electric field mode represented by in-plane switching (IPS) mode or fringe field switching (FFS) mode.
Among these modes, IPS mode is a mode in which the direction of electric field applied to liquid crystal is substantially parallel to a substrate. IPS mode is advantageous over TN mode or the like in that IPS mode can improve viewing angle characteristics.
However, in such a liquid crystal device, pixel electrodes made of a transparent conductive material such as indium tin oxide (ITO) or the like and a common electrode for generating a transverse electric field between the common electrode and the pixel electrodes are disposed in the same layer. Liquid crystal molecules located above the pixel electrodes are not sufficiently driven, resulting in a reduction in transmittance or the like.
With regard to this point, FFS mode is advantageous in that, since a layer in which a common electrode is disposed is below a layer in which pixel electrodes are disposed, a transverse electric field can be applied to liquid crystal molecules located above the pixel electrodes, thereby sufficiently driving the liquid crystal molecules located at these positions. As a result, FFS mode has an advantage over the above-described IPS mode because FFS mode can improve transmittance and the like.
Liquid crystal devices in the above-described FFS mode are described in JP-A-2001-235763 and JP-A-2002-182230.
The liquid crystal devices described in these patent documents are liquid crystal devices in FFS mode in which amorphous silicon ((α-Si) thin film transistors (TFTs) are used. In the liquid crystal device described in the latter patent document (JP-A-2002-182230), pixel electrodes have a vertically long shape (vertical stripes) with a long side extending in the direction in which data bus lines extend and a short side extending in the direction in which gate bus lines extend. Each of the pixel electrodes has a plurality of slits for generating a fringe field (transverse electric field) between the pixel electrodes and a counter electrode (common electrode) disposed in a lower layer.
In these liquid crystal devices, colored layers corresponding to the primary colors red (R), green (G), and blue (B) are generally provided in corresponding pixel electrodes. A voltage according to a grayscale level is applied to each of the pixel electrodes corresponding to the colors to adjust the transmittance of the pixel electrodes, thereby displaying a complex intermediate color. In recent years, an image display apparatus capable of displaying a wide range of colors is proposed. Such an image display apparatus has, besides the colored layers corresponding to the three primary colors R, G, and B, an additional colored layer corresponding to cyan (C), which is a complementary color. An exemplary image display apparatus is described in JP-A-2001-306023.
In the liquid crystal device described in JP-A-2002-182230, the pixel electrodes are vertical stripes, and slits are arranged at a predetermined angle so as to be symmetrical about the center of each of the pixel electrodes in the long-side direction. As a result, the number of slits is increased.
In a general liquid crystal device in FFS mode, when liquid crystal is driven, application of a fringe field is changed in the vicinity of one of two ends of each of slits in a pixel electrode, compared with other regions away from the end of the slit. This results in a generation of a domain region where liquid crystal molecules are hardly driven (liquid crystal alignment abnormal region). In such a domain region, brightness is reduced, and the domain region seems as a dark region when displayed. Phenomenally, the number of such domain regions is the number of slits, and such domain regions are generated in an alternating zigzag pattern in the adjacent slits. Since the pixel structure in the liquid crystal device described in JP-A-2002-182230 is such that the number of slits is large, domain regions that do not contribute to brightness increases in number, and hence, the transmittance of the liquid crystal device is greatly reduced.